From 61f3dee4af09528997a970280da240577bf60721 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:40 +1100 Subject: fs: dcache reduce dput locking It is possible to run dput without taking data structure locks up-front. In many cases where we don't kill the dentry anyway, these locks are not required. Signed-off-by: Nick Piggin --- fs/dcache.c | 52 +++++++++++++++++++++++----------------------------- 1 file changed, 23 insertions(+), 29 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index bf6294a20f0e..98a05696593e 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -323,35 +323,16 @@ repeat: if (dentry->d_count == 1) might_sleep(); spin_lock(&dentry->d_lock); - if (IS_ROOT(dentry)) - parent = NULL; - else - parent = dentry->d_parent; - if (dentry->d_count == 1) { - if (!spin_trylock(&dcache_inode_lock)) { -drop2: - spin_unlock(&dentry->d_lock); - goto repeat; - } - if (parent && !spin_trylock(&parent->d_lock)) { - spin_unlock(&dcache_inode_lock); - goto drop2; - } - } - dentry->d_count--; - if (dentry->d_count) { + BUG_ON(!dentry->d_count); + if (dentry->d_count > 1) { + dentry->d_count--; spin_unlock(&dentry->d_lock); - if (parent) - spin_unlock(&parent->d_lock); return; } - /* - * AV: ->d_delete() is _NOT_ allowed to block now. - */ if (dentry->d_op && dentry->d_op->d_delete) { if (dentry->d_op->d_delete(dentry)) - goto unhash_it; + goto kill_it; } /* Unreachable? Get rid of it */ @@ -362,17 +343,30 @@ drop2: dentry->d_flags |= DCACHE_REFERENCED; dentry_lru_add(dentry); - spin_unlock(&dentry->d_lock); - if (parent) - spin_unlock(&parent->d_lock); - spin_unlock(&dcache_inode_lock); + dentry->d_count--; + spin_unlock(&dentry->d_lock); return; -unhash_it: - __d_drop(dentry); kill_it: + if (!spin_trylock(&dcache_inode_lock)) { +relock: + spin_unlock(&dentry->d_lock); + cpu_relax(); + goto repeat; + } + if (IS_ROOT(dentry)) + parent = NULL; + else + parent = dentry->d_parent; + if (parent && !spin_trylock(&parent->d_lock)) { + spin_unlock(&dcache_inode_lock); + goto relock; + } + dentry->d_count--; /* if dentry was on the d_lru list delete it from there */ dentry_lru_del(dentry); + /* if it was on the hash (d_delete case), then remove it */ + __d_drop(dentry); dentry = d_kill(dentry, parent); if (dentry) goto repeat; -- cgit v1.2.3-59-g8ed1b